title: Platelets and coagulation proteins.
abstract: Platelets participate in hemostasis in part by their complex interrelationships with coagulation proteins. Several intrinsic platelet proteins are present in alpha-granules (fibrinogen, factor V, factor VIII antigen, platelet factor 4), in the cytosol (factor XIII), or in the membrane fraction (factor XI). Platelets also contribute to surface-mediated zymogen activations of plasma factors XII, XI, X, and prothrombin and bind several coagulation proteins including factor Xa, thrombin, and fibrinogen. Finally, platelets can protect coagulation enzymes (factors XIa and Xa) from inactivation by plasma proteinase inhibitors. Thereby intrinsic coagulation reactions occur preferentially on the platelet surface leading to fibrin formation within and around platelet plugs.
mesh_terms: D001779:Blood Coagulation Factors / Q000502:physiology*; D001792:Blood Platelets / Q000502:physiology*; D004789:Enzyme Activation; D005165:Factor V / Q000502:physiology; D005169:Factor VIII / Q000502:physiology; D005170:Factor X / Q000502:physiology; D005172:Factor XI / Q000502:physiology; D005337:Fibrin / Q000502:physiology; D005340:Fibrinogen / Q000502:physiology; D006801:Humans; D011516:Prothrombin / Q000502:physiology; D013917:Thrombin / Q000502:physiology
chemical_list: D001779:Blood Coagulation Factors; D005165:Factor V; D011516:Prothrombin; D005169:Factor VIII; D005170:Factor X; D005337:Fibrin; D005340:Fibrinogen; D005172:Factor XI; D013917:Thrombin